Laser gyroscopes utilizing four frequencies to avoid locking of waves traveling in opposite directions around a laser gyro ring resonator path have been built of the type shown, for example, in U.S. Pat. Nos. 3,741,657 and 3,854,819 by Andringa. It has been found that such gyroscopes can exhibit thermal drift in the apparent output due to the relative motion of scattering centers on or in optiical components of the laser gyro resonator. In the case of these patents, the scattering centers are mainly the surfaces of any solid element, such as used for magnetic bias. Attempts to replace Faraday rotation units in the path of the laser by a magnetic mirror have heretofore been unsatisfactory due to the high losses in the magnetic mirrors. Such a mirror shown, for example, in U.S. Pat. No. 3,851,973 is undesirable due to the very large absorption of light waves incident on the mirror. In addition, such a system utilizes the transverse Kerr magneto-optic effect which gives rise to nonreciprocal phase shifts only for linearly polarized components, and thus is not suitable for gyro systems employing circulary polarized waves.